The problems of scale formation and attendant effects have troubled water systems for years. For instance, scale tends to accumulate on internal walls of various water systems, such as boiler and cooling systems, and thereby materially lessens the operational efficiency of the system.
Deposits in lines, heat exchange equipment, etc., may originate from several causes. For example, precipitation of calcium phosphate in the water system leads to an accumulation of this scale imparting compound along or around the metal surfaces which contact the flowing water circulating through the system. In this manner, heat transfer functions of the particular system are severely impeded.
Recently, due to the popularity of cooling system treatments requiring high levels of orthophosphate ion to promote passivation of the metallurgy in contact with the system water, it has become critically important to control calcium phosphate crystallization so that relatively high levels of orthophosphate may be maintained in the system water to achieve the desired passivation effect without resulting in fouling or impeded heat transfer functions which would normally be caused by calcium phosphate deposition.
Although boiler systems are commonly treated with sophisticated hardness removal devices such as ion exchange units and influent coagulation and filtration devices, calcium phosphate scale can also be encountered due to the residual calcium hardness left in the influent water. As is obvious, the deposition of such calcium phosphate scale on the structural parts of a steam generating system causes poor circulation and lower heat transfer capacity, resulting in overall loss in heat transfer efficiency of the system.